A major concern at every stage in the manufacture of electronic components is contamination. Control of contamination is critical to product quality, and an extremely high level of cleanliness and purity in the manufacturing environment is needed for obtaining acceptable product yield and maintaining profitability. These requirements are particularly acute in the manufacture of very high density circuitry as well as in ultra-precision bearings, recording heads and LCD displays.
Sources of contamination include the manufacturing facility, personnel and processing equipment. In many cases, contamination can be lowered to acceptable levels by the use of "clean room" techniques such as isolation, air filtration, special equipment and special clothing and body coverings to avoid contact between the operator and the manufacturing materials. With ultra-high precision manufacturing, however, the highest levels at which defects can be tolerated are particularly low and control over sources of contamination is even more critical.
Ammonia presents particular difficulties, since liquid ammonia contains both solid and volatile impurities, many of which are damaging to electronic components if present during the manufacturing process. The impurities level and content may vary widely depending on the source as well as the handling method, and all such impurities must be removed before the ammonia can be used in electronic component production lines.
To meet this standard, production facilities have had to obtain high-quality ammonia at considerable cost from the limited sources which are able to supply ammonia at an acceptable grade. Only qualified suppliers can be used, and new suppliers must be qualified before their product can be accepted. This cost and the lack of flexibility add considerably to the cost of the components.
Further difficulties arise in meeting Department of Transportation regulations. Ammonium hydroxide are shipped at concentrations no higher than 30%.
Clearly there is a need for a reliable means of supplying ammonia at a purity level which will produce a high yield of acceptable product in ultra-high precision components, and which can meet the requirements of advancing electronics technology.